[ThinLTO] Implement summary visualizer

Differential revision: https://reviews.llvm.org/D41297


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323062 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/ModuleSummaryIndex.h

@@ -69,9 +69,27 @@ class GlobalValueSummary;
 using GlobalValueSummaryList = std::vector<std::unique_ptr<GlobalValueSummary>>;
 
 struct GlobalValueSummaryInfo {
-  /// The GlobalValue corresponding to this summary. This is only used in
-  /// per-module summaries.
-  const GlobalValue *GV = nullptr;
+  union NameOrGV {
+    NameOrGV(bool IsAnalysis) {
+      if (IsAnalysis)
+        GV = nullptr;
+      else
+        Name = "";
+    }
+
+    /// The GlobalValue corresponding to this summary. This is only used in
+    /// per-module summaries, when module analysis is being run.
+    const GlobalValue *GV;
+
+    /// Summary string representation. This StringRef points to BC module
+    /// string table and is valid until module data is stored in memory.
+    /// This is guaranteed to happen until runThinLTOBackend function is
+    /// called, so it is safe to use this field during thin link. This field
+    /// is only valid if summary index was loaded from BC file.
+    StringRef Name;
+  } U;
+
+  GlobalValueSummaryInfo(bool IsAnalysis) : U(IsAnalysis) {}
 
   /// List of global value summary structures for a particular value held
   /// in the GlobalValueMap. Requires a vector in the case of multiple
@@ -91,32 +109,60 @@ using GlobalValueSummaryMapTy =
 /// Struct that holds a reference to a particular GUID in a global value
 /// summary.
 struct ValueInfo {
-  const GlobalValueSummaryMapTy::value_type *Ref = nullptr;
+  PointerIntPair<const GlobalValueSummaryMapTy::value_type *, 1, bool>
+      RefAndFlag;
 
   ValueInfo() = default;
-  ValueInfo(const GlobalValueSummaryMapTy::value_type *Ref) : Ref(Ref) {}
+  ValueInfo(bool IsAnalysis, const GlobalValueSummaryMapTy::value_type *R) {
+    RefAndFlag.setPointer(R);
+    RefAndFlag.setInt(IsAnalysis);
+  }
 
-  operator bool() const { return Ref; }
+  operator bool() const { return getRef(); }
 
-  GlobalValue::GUID getGUID() const { return Ref->first; }
-  const GlobalValue *getValue() const { return Ref->second.GV; }
+  GlobalValue::GUID getGUID() const { return getRef()->first; }
+  const GlobalValue *getValue() const {
+    assert(isFromAnalysis());
+    return getRef()->second.U.GV;
+  }
 
   ArrayRef<std::unique_ptr<GlobalValueSummary>> getSummaryList() const {
-    return Ref->second.SummaryList;
+    return getRef()->second.SummaryList;
+  }
+
+  StringRef name() const {
+    return isFromAnalysis() ? getRef()->second.U.GV->getName()
+                            : getRef()->second.U.Name;
+  }
+
+  bool isFromAnalysis() const { return RefAndFlag.getInt(); }
+
+  const GlobalValueSummaryMapTy::value_type *getRef() const {
+    return RefAndFlag.getPointer();
   }
 };
 
 template <> struct DenseMapInfo<ValueInfo> {
   static inline ValueInfo getEmptyKey() {
-    return ValueInfo((GlobalValueSummaryMapTy::value_type *)-1);
+    return ValueInfo(false, (GlobalValueSummaryMapTy::value_type *)-8);
   }
 
   static inline ValueInfo getTombstoneKey() {
-    return ValueInfo((GlobalValueSummaryMapTy::value_type *)-2);
+    return ValueInfo(false, (GlobalValueSummaryMapTy::value_type *)-16);
+  }
+
+  static inline bool isSpecialKey(ValueInfo V) {
+    return V == getTombstoneKey() || V == getEmptyKey();
   }
 
-  static bool isEqual(ValueInfo L, ValueInfo R) { return L.Ref == R.Ref; }
-  static unsigned getHashValue(ValueInfo I) { return (uintptr_t)I.Ref; }
+  static bool isEqual(ValueInfo L, ValueInfo R) {
+    // We are not supposed to mix ValueInfo(s) with different analysis flag
+    // in a same container.
+    assert(isSpecialKey(L) || isSpecialKey(R) ||
+           (L.isFromAnalysis() == R.isFromAnalysis()));
+    return L.getRef() == R.getRef();
+  }
+  static unsigned getHashValue(ValueInfo I) { return (uintptr_t)I.getRef(); }
 };
 
 /// \brief Function and variable summary information to aid decisions and
@@ -619,6 +665,11 @@ private:
   /// considered live.
   bool WithGlobalValueDeadStripping = false;
 
+  /// If true then we're performing analysis of IR module, filling summary
+  /// accordingly. The value of 'false' means we're reading summary from
+  /// BC or YAML source. Affects the type of value stored in NameOrGV union
+  bool IsAnalysis;
+
   std::set<std::string> CfiFunctionDefs;
   std::set<std::string> CfiFunctionDecls;
 
@@ -627,10 +678,16 @@ private:
 
   GlobalValueSummaryMapTy::value_type *
   getOrInsertValuePtr(GlobalValue::GUID GUID) {
-    return &*GlobalValueMap.emplace(GUID, GlobalValueSummaryInfo{}).first;
+    return &*GlobalValueMap.emplace(GUID, GlobalValueSummaryInfo(IsAnalysis)).first;
   }
 
 public:
+  // See IsAnalysis variable comment.
+  ModuleSummaryIndex(bool IsPerformingAnalysis)
+      : IsAnalysis(IsPerformingAnalysis) {}
+
+  bool isPerformingAnalysis() const { return IsAnalysis; }
+
   gvsummary_iterator begin() { return GlobalValueMap.begin(); }
   const_gvsummary_iterator begin() const { return GlobalValueMap.begin(); }
   gvsummary_iterator end() { return GlobalValueMap.end(); }
@@ -652,19 +709,28 @@ public:
   /// Return a ValueInfo for GUID if it exists, otherwise return ValueInfo().
   ValueInfo getValueInfo(GlobalValue::GUID GUID) const {
     auto I = GlobalValueMap.find(GUID);
-    return ValueInfo(I == GlobalValueMap.end() ? nullptr : &*I);
+    return ValueInfo(IsAnalysis, I == GlobalValueMap.end() ? nullptr : &*I);
   }
 
   /// Return a ValueInfo for \p GUID.
   ValueInfo getOrInsertValueInfo(GlobalValue::GUID GUID) {
-    return ValueInfo(getOrInsertValuePtr(GUID));
+    return ValueInfo(IsAnalysis, getOrInsertValuePtr(GUID));
+  }
+
+  /// Return a ValueInfo for \p GUID setting value \p Name. 
+  ValueInfo getOrInsertValueInfo(GlobalValue::GUID GUID, StringRef Name) {
+    assert(!IsAnalysis);
+    auto VP = getOrInsertValuePtr(GUID);
+    VP->second.U.Name = Name;
+    return ValueInfo(IsAnalysis, VP);
   }
 
   /// Return a ValueInfo for \p GV and mark it as belonging to GV.
   ValueInfo getOrInsertValueInfo(const GlobalValue *GV) {
+    assert(IsAnalysis);
     auto VP = getOrInsertValuePtr(GV->getGUID());
-    VP->second.GV = GV;
-    return ValueInfo(VP);
+    VP->second.U.GV = GV;
+    return ValueInfo(IsAnalysis, VP);
   }
 
   /// Return the GUID for \p OriginalId in the OidGuidMap.
@@ -692,7 +758,7 @@ public:
     addOriginalName(VI.getGUID(), Summary->getOriginalName());
     // Here we have a notionally const VI, but the value it points to is owned
     // by the non-const *this.
-    const_cast<GlobalValueSummaryMapTy::value_type *>(VI.Ref)
+    const_cast<GlobalValueSummaryMapTy::value_type *>(VI.getRef())
         ->second.SummaryList.push_back(std::move(Summary));
   }
 
@@ -823,6 +889,9 @@ public:
   /// Summary).
   void collectDefinedGVSummariesPerModule(
       StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries) const;
+
+  /// Export summary to dot file for GraphViz.
+  void exportToDot(raw_ostream& OS) const;
 };
 
 } // end namespace llvm

include/llvm/IR/ModuleSummaryIndexYAML.h

@@ -207,7 +207,8 @@ template <> struct CustomMappingTraits<GlobalValueSummaryMapTy> {
       io.setError("key not an integer");
       return;
     }
-    auto &Elem = V[KeyInt];
+    auto P = V.emplace(KeyInt, /*IsAnalysis=*/false);
+    auto &Elem = (*P.first).second;
     for (auto &FSum : FSums) {
       Elem.SummaryList.push_back(llvm::make_unique<FunctionSummary>(
           GlobalValueSummary::GVFlags(

lib/Analysis/ModuleSummaryAnalysis.cpp

@@ -372,7 +372,7 @@ ModuleSummaryIndex llvm::buildModuleSummaryIndex(
     std::function<BlockFrequencyInfo *(const Function &F)> GetBFICallback,
     ProfileSummaryInfo *PSI) {
   assert(PSI);
-  ModuleSummaryIndex Index;
+  ModuleSummaryIndex Index(/*IsPerformingAnalysis=*/true);
 
   // Identify the local values in the llvm.used and llvm.compiler.used sets,
   // which should not be exported as they would then require renaming and

lib/Bitcode/Reader/BitcodeReader.cpp

@@ -4813,8 +4813,12 @@ void ModuleSummaryIndexBitcodeReader::setValueGUID(
   if (PrintSummaryGUIDs)
     dbgs() << "GUID " << ValueGUID << "(" << OriginalNameID << ") is "
            << ValueName << "\n";
-  ValueIdToValueInfoMap[ValueID] =
-      std::make_pair(TheIndex.getOrInsertValueInfo(ValueGUID), OriginalNameID);
+  
+  // UseStrtab is false for legacy summary formats and value names are
+  // created on stack. We can't use them outside of parseValueSymbolTable.
+  ValueIdToValueInfoMap[ValueID] = std::make_pair(
+      TheIndex.getOrInsertValueInfo(ValueGUID, UseStrtab ? ValueName : ""),
+      OriginalNameID);
 }
 
 // Specialized value symbol table parser used when reading module index
@@ -5679,7 +5683,8 @@ Expected<std::unique_ptr<ModuleSummaryIndex>> BitcodeModule::getSummary() {
   BitstreamCursor Stream(Buffer);
   Stream.JumpToBit(ModuleBit);
 
-  auto Index = llvm::make_unique<ModuleSummaryIndex>();
+  auto Index =
+      llvm::make_unique<ModuleSummaryIndex>(/*IsPerformingAnalysis=*/false);
   ModuleSummaryIndexBitcodeReader R(std::move(Stream), Strtab, *Index,
                                     ModuleIdentifier, 0);
 

lib/IR/ModuleSummaryIndex.cpp

@@ -14,6 +14,7 @@
 
 #include "llvm/IR/ModuleSummaryIndex.h"
 #include "llvm/ADT/StringMap.h"
+#include "llvm/Support/Path.h"
 using namespace llvm;
 
 // Collect for the given module the list of function it defines
@@ -69,3 +70,246 @@ bool ModuleSummaryIndex::isGUIDLive(GlobalValue::GUID GUID) const {
       return true;
   return false;
 }
+
+namespace {
+struct Attributes {
+  void add(const Twine &Name, const Twine &Value,
+           const Twine &Comment = Twine());
+  std::string getAsString() const;
+
+  std::vector<std::string> Attrs;
+  std::string Comments;
+};
+
+struct Edge {
+  uint64_t SrcMod;
+  int Hotness;
+  GlobalValue::GUID Src;
+  GlobalValue::GUID Dst;
+};
+}
+
+void Attributes::add(const Twine &Name, const Twine &Value,
+                     const Twine &Comment) {
+  std::string A = Name.str();
+  A += "=\"";
+  A += Value.str();
+  A += "\"";
+  Attrs.push_back(A);
+  if (!Comment.isTriviallyEmpty()) {
+    if (Comments.empty())
+      Comments = " // ";
+    else
+      Comments += ", ";
+    Comments += Comment.str();
+  }
+}
+
+std::string Attributes::getAsString() const {
+  if (Attrs.empty())
+    return "";
+
+  std::string Ret = "[";
+  for (auto &A : Attrs)
+    Ret += A + ",";
+  Ret.pop_back();
+  Ret += "];";
+  Ret += Comments;
+  return Ret;
+}
+
+static std::string linkageToString(GlobalValue::LinkageTypes LT) {
+  switch (LT) {
+  case GlobalValue::ExternalLinkage:
+    return "extern";
+  case GlobalValue::AvailableExternallyLinkage:
+    return "av_ext";
+  case GlobalValue::LinkOnceAnyLinkage:
+    return "linkonce";
+  case GlobalValue::LinkOnceODRLinkage:
+    return "linkonce_odr";
+  case GlobalValue::WeakAnyLinkage:
+    return "weak";
+  case GlobalValue::WeakODRLinkage:
+    return "weak_odr";
+  case GlobalValue::AppendingLinkage:
+    return "appending";
+  case GlobalValue::InternalLinkage:
+    return "internal";
+  case GlobalValue::PrivateLinkage:
+    return "private";
+  case GlobalValue::ExternalWeakLinkage:
+    return "extern_weak";
+  case GlobalValue::CommonLinkage:
+    return "common";
+  }
+
+  return "<unknown>";
+}
+
+static std::string fflagsToString(FunctionSummary::FFlags F) {
+  auto FlagValue = [](unsigned V) { return V ? '1' : '0'; };
+  char FlagRep[] = {FlagValue(F.ReadNone), FlagValue(F.ReadOnly),
+                    FlagValue(F.NoRecurse), FlagValue(F.ReturnDoesNotAlias), 0};
+
+  return FlagRep;
+}
+
+// Get string representation of function instruction count and flags.
+static std::string getSummaryAttributes(GlobalValueSummary* GVS) {
+  auto *FS = dyn_cast_or_null<FunctionSummary>(GVS);
+  if (!FS)
+    return "";
+
+  return std::string("inst: ") + std::to_string(FS->instCount()) +
+         ", ffl: " + fflagsToString(FS->fflags());
+}
+
+static std::string getNodeVisualName(const ValueInfo &VI) {
+  return VI.name().empty() ? std::string("@") + std::to_string(VI.getGUID())
+                           : VI.name().str();
+}
+
+static std::string getNodeLabel(const ValueInfo &VI, GlobalValueSummary *GVS) {
+  if (isa<AliasSummary>(GVS))
+    return getNodeVisualName(VI);
+
+  std::string Attrs = getSummaryAttributes(GVS);
+  std::string Label =
+      getNodeVisualName(VI) + "|" + linkageToString(GVS->linkage());
+  if (!Attrs.empty())
+    Label += std::string(" (") + Attrs + ")";
+  Label += "}";
+
+  return Label;
+}
+
+// Write definition of external node, which doesn't have any
+// specific module associated with it. Typically this is function
+// or variable defined in native object or library.
+static void defineExternalNode(raw_ostream &OS, const char *Pfx,
+                               const ValueInfo &VI) {
+  auto StrId = std::to_string(VI.getGUID());
+  OS << "  " << StrId << " [label=\"" << getNodeVisualName(VI)
+     << "\"]; // defined externally\n";
+}
+
+void ModuleSummaryIndex::exportToDot(raw_ostream& OS) const {
+  std::vector<Edge> CrossModuleEdges;
+  DenseMap<GlobalValue::GUID, std::vector<uint64_t>> NodeMap;
+  StringMap<GVSummaryMapTy> ModuleToDefinedGVS;
+  collectDefinedGVSummariesPerModule(ModuleToDefinedGVS);
+
+  // Get node identifier in form MXXX_<GUID>. The MXXX prefix is required,
+  // because we may have multiple linkonce functions summaries.
+  auto NodeId = [](uint64_t ModId, GlobalValue::GUID Id) {
+    return ModId == (uint64_t)-1 ? std::to_string(Id)
+                                 : std::string("M") + std::to_string(ModId) +
+                                       "_" + std::to_string(Id);
+  };
+
+  auto DrawEdge = [&](const char *Pfx, int SrcMod, GlobalValue::GUID SrcId,
+                      int DstMod, GlobalValue::GUID DstId, int TypeOrHotness) {
+    // 0 corresponds to alias edge, 1 to ref edge, 2 to call with unknown
+    // hotness, ...
+    TypeOrHotness += 2;
+    static const char *EdgeAttrs[] = {
+        " [style=dotted]; // alias",
+        " [style=dashed]; // ref",
+        " // call (hotness : Unknown)",
+        " [color=blue]; // call (hotness : Cold)",
+        " // call (hotness : None)",
+        " [color=brown]; // call (hotness : Hot)",
+        " [style=bold,color=red]; // call (hotness : Critical)"};
+
+    assert(static_cast<size_t>(TypeOrHotness) <
+           sizeof(EdgeAttrs) / sizeof(EdgeAttrs[0]));
+    OS << Pfx << NodeId(SrcMod, SrcId) << " -> " << NodeId(DstMod, DstId)
+       << EdgeAttrs[TypeOrHotness] << "\n";
+  };
+
+  OS << "digraph Summary {\n";
+  for (auto &ModIt : ModuleToDefinedGVS) {
+    auto ModId = getModuleId(ModIt.first());
+    OS << "  // Module: " << ModIt.first() << "\n";
+    OS << "  subgraph cluster_" << std::to_string(ModId) << " {\n";
+    OS << "    style = filled;\n";
+    OS << "    color = lightgrey;\n";
+    OS << "    label = \"" << sys::path::filename(ModIt.first()) << "\";\n";
+    OS << "    node [style=filled,fillcolor=lightblue];\n";
+
+    auto &GVSMap = ModIt.second;
+    auto Draw = [&](GlobalValue::GUID IdFrom, GlobalValue::GUID IdTo, int Hotness) {
+      if (!GVSMap.count(IdTo)) {
+        CrossModuleEdges.push_back({ModId, Hotness, IdFrom, IdTo});
+        return;
+      }
+      DrawEdge("    ", ModId, IdFrom, ModId, IdTo, Hotness);
+    };
+
+    for (auto &SummaryIt : GVSMap) {
+      NodeMap[SummaryIt.first].push_back(ModId);
+      auto Flags = SummaryIt.second->flags();
+      Attributes A;
+      if (isa<FunctionSummary>(SummaryIt.second)) {
+        A.add("shape", "record", "function");
+      } else if (isa<AliasSummary>(SummaryIt.second)) {
+        A.add("style", "dotted,filled", "alias");
+        A.add("shape", "box");
+      } else {
+        A.add("shape", "Mrecord", "variable");
+      }
+
+      auto VI = getValueInfo(SummaryIt.first);
+      A.add("label", getNodeLabel(VI, SummaryIt.second));
+      if (!Flags.Live)
+        A.add("fillcolor", "red", "dead");
+      else if (Flags.NotEligibleToImport)
+        A.add("fillcolor", "yellow", "not eligible to import");
+
+      OS << "    " << NodeId(ModId, SummaryIt.first) << " " << A.getAsString()
+         << "\n";
+    }
+    OS << "    // Edges:\n";
+
+    for (auto &SummaryIt : GVSMap) {
+      auto *GVS = SummaryIt.second;
+      for (auto &R : GVS->refs())
+        Draw(SummaryIt.first, R.getGUID(), -1);
+
+      if (auto *AS = dyn_cast_or_null<AliasSummary>(SummaryIt.second)) {
+        auto AliaseeOrigId = AS->getAliasee().getOriginalName();
+        auto AliaseeId = getGUIDFromOriginalID(AliaseeOrigId);
+
+        Draw(SummaryIt.first, AliaseeId ? AliaseeId : AliaseeOrigId, -2);
+        continue;
+      }
+
+      if (auto *FS = dyn_cast_or_null<FunctionSummary>(SummaryIt.second))
+        for (auto &CGEdge : FS->calls())
+          Draw(SummaryIt.first, CGEdge.first.getGUID(),
+               static_cast<int>(CGEdge.second.Hotness));
+    }
+    OS << "  }\n";
+  }
+
+  for (auto &E : CrossModuleEdges) {
+    auto &ModList = NodeMap[E.Dst];
+    if (ModList.empty()) {
+      defineExternalNode(OS, "  ", getValueInfo(E.Dst));
+      // Add fake module to the list to draw an edge to an external node
+      // in the loop below.
+      ModList.push_back(-1);
+    }
+    for (auto DstMod : ModList)
+      // The edge representing call or ref is drawn to every module where target
+      // symbol is defined. When target is a linkonce symbol there can be
+      // multiple edges representing a single call or ref, both intra-module and
+      // cross-module. As we've already drawn all intra-module edges before we
+      // skip it here.
+      if (DstMod != E.SrcMod)
+        DrawEdge("  ", E.SrcMod, E.Src, DstMod, E.Dst, E.Hotness);
+  }
+
+  OS << "}";
+}

lib/LTO/LTO.cpp

@@ -388,7 +388,8 @@ LTO::RegularLTOState::RegularLTOState(unsigned ParallelCodeGenParallelismLevel,
       Ctx(Conf), CombinedModule(llvm::make_unique<Module>("ld-temp.o", Ctx)),
       Mover(llvm::make_unique<IRMover>(*CombinedModule)) {}
 
-LTO::ThinLTOState::ThinLTOState(ThinBackend Backend) : Backend(Backend) {
+LTO::ThinLTOState::ThinLTOState(ThinBackend Backend)
+    : Backend(Backend), CombinedIndex(/*IsPeformingAnalysis*/ false) {
   if (!Backend)
     this->Backend =
         createInProcessThinBackend(llvm::heavyweight_hardware_concurrency());

lib/LTO/LTOBackend.cpp

@@ -103,6 +103,12 @@ Error Config::addSaveTemps(std::string OutputFileName,
     if (EC)
       reportOpenError(Path, EC.message());
     WriteIndexToFile(Index, OS);
+
+    Path = OutputFileName + "index.dot";
+    raw_fd_ostream OSDot(Path, EC, sys::fs::OpenFlags::F_None);
+    if (EC)
+      reportOpenError(Path, EC.message());
+    Index.exportToDot(OSDot);
     return true;
   };
 

lib/LTO/ThinLTOCodeGenerator.cpp

@@ -592,7 +592,7 @@ std::unique_ptr<TargetMachine> TargetMachineBuilder::create() const {
  */
 std::unique_ptr<ModuleSummaryIndex> ThinLTOCodeGenerator::linkCombinedIndex() {
   std::unique_ptr<ModuleSummaryIndex> CombinedIndex =
-      llvm::make_unique<ModuleSummaryIndex>();
+      llvm::make_unique<ModuleSummaryIndex>(/*IsPeformingAnalysis=*/false);
   uint64_t NextModuleId = 0;
   for (auto &ModuleBuffer : Modules) {
     if (Error Err = readModuleSummaryIndex(ModuleBuffer.getMemBuffer(),

lib/Transforms/IPO/FunctionImport.cpp

@@ -231,7 +231,7 @@ updateValueInfoForIndirectCalls(const ModuleSummaryIndex &Index, ValueInfo VI) {
   // it, rather than needing to perform this mapping on each walk.
   auto GUID = Index.getGUIDFromOriginalID(VI.getGUID());
   if (GUID == 0)
-    return nullptr;
+    return ValueInfo();
   return Index.getValueInfo(GUID);
 }
 
@@ -517,7 +517,7 @@ void llvm::computeDeadSymbols(
     for (auto &S : Entry.second.SummaryList)
       if (S->isLive()) {
         DEBUG(dbgs() << "Live root: " << Entry.first << "\n");
-        Worklist.push_back(ValueInfo(&Entry));
+        Worklist.push_back(ValueInfo(/*IsAnalysis=*/false, &Entry));
         ++LiveSymbols;
         break;
       }

lib/Transforms/IPO/LowerTypeTests.cpp

@@ -1529,7 +1529,7 @@ LowerTypeTestsModule::LowerTypeTestsModule(
 }
 
 bool LowerTypeTestsModule::runForTesting(Module &M) {
-  ModuleSummaryIndex Summary;
+  ModuleSummaryIndex Summary(/*IsPerformingAnalysis=*/false);
 
   // Handle the command-line summary arguments. This code is for testing
   // purposes only, so we handle errors directly.

lib/Transforms/IPO/WholeProgramDevirt.cpp

@@ -584,7 +584,7 @@ PreservedAnalyses WholeProgramDevirtPass::run(Module &M,
 bool DevirtModule::runForTesting(
     Module &M, function_ref<AAResults &(Function &)> AARGetter,
     function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter) {
-  ModuleSummaryIndex Summary;
+  ModuleSummaryIndex Summary(/*IsPerformingAnalysis=*/false);
 
   // Handle the command-line summary arguments. This code is for testing
   // purposes only, so we handle errors directly.

test/ThinLTO/X86/Inputs/dot-dumper.ll

@@ -0,0 +1,20 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@A = local_unnamed_addr global i32 10, align 4
+@B = local_unnamed_addr global i32 20, align 4
+
+; Function Attrs: norecurse nounwind readonly uwtable
+define i32 @foo() local_unnamed_addr #0 {
+  %1 = load i32, i32* @B, align 4
+  %2 = load i32, i32* @A, align 4
+  %3 = add nsw i32 %2, %1
+  ret i32 %3
+}
+
+; Function Attrs: norecurse nounwind readnone uwtable
+define i32 @bar() local_unnamed_addr {
+  ret i32 42
+}
+
+attributes #0 = { noinline }

test/ThinLTO/X86/dot-dumper.ll

@@ -0,0 +1,54 @@
+; RUN: opt -module-summary %s -o %t1.bc
+; RUN: opt -module-summary %p/Inputs/dot-dumper.ll -o %t2.bc
+; RUN: llvm-lto2 run -save-temps %t1.bc %t2.bc -o %t3 \
+; RUN:  -r=%t1.bc,main,px \
+; RUN:  -r=%t1.bc,main_alias,p \
+; RUN:  -r=%t1.bc,foo, \
+; RUN:  -r=%t1.bc,A, \
+; RUN:  -r=%t2.bc,foo,p \
+; RUN:  -r=%t2.bc,bar,p \
+; RUN:  -r=%t2.bc,A,p \
+; RUN:  -r=%t2.bc,B,p
+; RUN: cat %t3.index.dot | FileCheck %s
+
+; CHECK:        digraph Summary
+; CHECK-NEXT:      Module:
+
+; CHECK-LABEL:     subgraph cluster_0
+; Node definitions can appear in any order, but they should go before edge list.
+; CHECK-DAG:         M0_[[MAIN_ALIAS:[0-9]+]] [{{.*}}main_alias{{.*}}]; // alias, dead
+; CHECK-DAG:         M0_[[MAIN:[0-9]+]] [{{.*}}main|extern{{.*}}]; // function
+; CHECK:             // Edges:
+; CHECK-NEXT:        M0_[[MAIN_ALIAS]] -> M0_[[MAIN]] [{{.*}}]; // alias
+
+; CHECK-LABEL:     subgraph cluster_1 {
+; CHECK:             M1_[[A:[0-9]+]] [{{.*}}A|extern{{.*}}]; // variable
+
+; CHECK-DAG:         M1_[[FOO:[0-9]+]] [{{.*}}foo|extern{{.*}}]; // function, not eligible to import
+; CHECK-DAG:         M1_[[B:[0-9]+]] [{{.*}}B|extern{{.*}}]; // variable
+; CHECK-DAG:         M1_[[BAR:[0-9]+]] [{{.*}}bar|extern{{.*}}]; // function, dead
+; CHECK:             Edges:
+
+; Order of edges in dot file is undefined
+; CHECK-DAG:         M1_[[FOO]] -> M1_[[B]] [{{.*}}]; // ref
+; CHECK-DAG:         M1_[[FOO]] -> M1_[[A]] [{{.*}}]; // ref
+; CHECK:           }
+
+; Cross-module edges
+; CHECK-DAG:       M0_[[MAIN]] -> M1_[[FOO]] // call
+; CHECK-DAG:       M0_[[MAIN]] -> M1_[[A]] [{{.*}}]; // ref
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@A = external local_unnamed_addr global i32, align 4
+
+; Function Attrs: nounwind uwtable
+define i32 @main() local_unnamed_addr {
+  %1 = tail call i32 (...) @foo()
+  %2 = load i32, i32* @A, align 4
+  %3 = add nsw i32 %2, %1
+  ret i32 %3
+}
+@main_alias = weak_odr alias i32 (), i32 ()* @main
+declare i32 @foo(...) local_unnamed_addr

tools/llvm-lto/llvm-lto.cpp

@@ -367,7 +367,7 @@ static void listSymbols(const TargetOptions &Options) {
 /// This is meant to enable testing of ThinLTO combined index generation,
 /// currently available via the gold plugin via -thinlto.
 static void createCombinedModuleSummaryIndex() {
-  ModuleSummaryIndex CombinedIndex;
+  ModuleSummaryIndex CombinedIndex(/*IsPerformingAnalysis=*/false);
   uint64_t NextModuleId = 0;
   for (auto &Filename : InputFilenames) {
     ExitOnError ExitOnErr("llvm-lto: error loading file '" + Filename + "': ");